The prognostic value of thyrotropin receptor antibody measurement in the early stages of treatment of Graves' disease with antithyroid drugs

In most trials, at least 50% of patients with Graves' disease treated with antithyroid drugs (ATD) relapse after achieving euthyroidism. At present, there are no definitive prognostic parameters available early in treatment to indicate those likely to achieve long-term remission. Because thyrotropin receptor antibodies (TRAb) are specific for Graves' disease, the possibility that their rate of change early in treatment (0 to 6 months) might be such an indicator was explored. TRAb were measured both as thyrotropin binding inhibitory immunoglobulins (TBII) and as thyroid-stimulating antibodies (TSAb) in 85 patients with untreated Graves' disease at 6-month intervals throughout their ATD treatment. The patients in the study were treated for a minimum period of 12 months and were categorized retrospectively into two groups depending on whether or not they remained in remission after ATD treatment. Remission was deemed as reached in patients who remained euthyroid for a minimum period of 15 months after cessation of ATD. The mean initial TBII and TSAb values in the nonremission group were significantly higher than in the remission group (p < 0.001 for both parameters). The rates of fall in mean TBII levels were similar for each group in the first 6 months of treatment, but while they continued to fall in the remission group over the next 6 to 12 months, mean values for the nonremission group plateaued and failed to fall to control levels within that period. These results indicate that changes in TRAb levels, measured either as TBII or TSAb, occur more rapidly in the second 6 months of treatment in patients who ultimately achieve remission than those who do not. If TBII fall to control levels by 12 months, the patient has at least a 70% chance of ultimately achieving remission with ATD treatment alone.